Stabilized mineral oil



Patented July 25, 1939 STABILHZED M'HNERAL' on.

Elmer William Cook, New York, N. Y., assignor to Tide Water AssociatedOil Company, Bayonne, N. 3., a corporation of Delaware No Drawing.Application December 4, 1936, .Serial No. 114,136

'7 Claims.

The useful service life of mineral oils, in re-- spect both of thecharacter and rapidity of deterioration, is influenced. by the serviceconditions obtaining during use. In some instances, as in thelubrication of internal combustion engines, high temperatures prevailand thin films of the oil are in continued and renewed contact with'hotmetal surfaces. Strongly oxidizing atmospheres may be encountered inother services where operatingtemperatures are the Same or may be lower.In the lubrication of steam turbines, the oil temperature is relativelylow but contacted metal surfaces or other operating conditions maycatalyze, promote or permit acid or sludge formation with eventualemulsification due to the presence of water. For transformer, cablewrapping or other electrical services, the foregoing or other factorsmay tend to occasion deterioration. I

Petroleum hydrocarbons oils may be improved in some respects by refiningmethods effective to remove or convert, at least in part, certaindeterioration inducing constituents vnormally present therein. Refiningwith chemicals frequently is employed, as by extraction with selectivesolventsoi the character of phenol, liquid sulfur dioxide,'nitro-benzine, furfural, and others well known in the art as well ascombinations thereof, by clay filtration, or by moderate treatment withsulfuric acid of less than fuming acid strength. More drastic refining,as by treatment with fuming sulfuric acid, may be resorted to when it isdesired to produce highly refined viscous hydrocarbon oils the so-calledtechnical white oils) from which substantially all, asphalticconstituents have been removed. The refined products, however, still areto an undesirable degree susceptible to oxidation, polymerization, orother chemical phenomena to which may be attributed observed impairmentof the oil resulting from or indicated by acid, gum, and sludgeformation, coior degradation, inordinate viscosity increase, or otherevidence of deterioration.

Accordingly, it has been proposed to further improve the service life ofvarious mineral hydrocarbon oils, and in particular lubricating or likeoils of petroleum origin, by the incorporation therewith of substancesor compounds having an inhibiting or retarding action in one or anotherrespect upon the deterioration of the oil. Many suggestions heretoforehave been made in this direction and a, number of compounds advanced fortrial as inhibitors some of which in greater or less degree have provedeffective. Discrepancies in results have been noted, however, both as tothe relative inhibiting effect of a given com pound with'difierent oilsin overcoming a parvalue of an inhibitor in one oil environment from itseffect in another. Thus, many compounds effective as anti-gum formingagents for cracked gasoline may be wholly without eiiect in petroleumlubricating oils. Again, certain inhibitors of value in preventingdeterioration of very highly refined turbine oils (the so-calledtechnical white oils) have proved quite inefi'ective in respect ofinhibiting action in less highly refined turbine oils.

The action of inhibitors, particularly in mineral hydrocarbon oilenvironments, appears, therefore, to be in a sense specific not only forcertain reactions but further with respect to the character of the oil,the nature and extent of the refining to which it has been subjected,and the service for which it is intended. The present invention isconcerned with and provides compounds of proven inhibiting action; butit is deemed undesirable and of little practical value to attempt orrely upon any prescribed theory in explanation of observed efiects orresults.

In its broad aspect, the present invention relates to the use ofinhibitors which I have discovered to be of marked utility in preventingthe deterioration of viscous or relatively viscous petroleum oils (ascontrasted with the less viscous or non-viscous distillate petroleumproducts such as gasoline and kerosene).

More specifically, an important object of the invention is to provideeffective .lnhibitors for lubricating and like oils of petroleum origin;which oils have been subjected in greater or less degree to conventionalmethods of refining other than drastic treatment of the characterresorted to for the production of water white viscous mineral oils (viz,technical white oils as prepared by extended treatment with heavy fumingsulfuric acid).

A further object of the invention is to provide, for the indicated use,inhibitors selected from those compounds of a di-arylamine designationconforming to'the general molecular structure R-NH-R' wherein both R andR. are polycyclic or condensed aromatic rings and wherein the moleculararrangement is anti-symmetrical.

It is likewise an object of the invention to improve, and to provideimproved, lubricating oils by incorporating therewith small amounts ofthe compounds which I have discovered to be of effective inhibitingaction.

Other objects and advantages will appear from the following descriptionof the invention and the illustrative examples presented hereinafter inorder that the invention may be more particularly ascertained. 7

Various tests have been devised and are available by which a comparativeevaluation of oils with respect to deterioration thereof in service maybe obtained in a relatively short period of time. Some of these testsare of longer duration than others, but have the advantage of affordinga perhaps more reliable laboratory criterion by which to judge therelative value of various inhibitors than extremely accelerated tests.

One such relatively prolonged test, which has proved of particularconvenience in, although not limited to, the evaluation of oils intendedfor such service as the lubrication of steam turbines, is the familiarFunk test. In this test, a measured quantity of oil and water(ordinarily 8 gallons of oil and 0.8 gallon of distilled water) iscontinuously circulated through a cast iron chamber under conditions ofviolent agitation, the oil being maintained at a temperature of 200 F.and air being passed continuously through the Bii as it circulates andre-circulates through the chamber. The length of time required to form1% (by volume) of sludge and emulsion as measured in a centrifugedsample is the criterion by which the relative service life of the oil ismeasured.

Illustrative of inhibitors according to the invention is the compoundalpha beta di-naphthyl amine which is an anti-symmetrical di-aryl aminehaving the structural formula:

which compound has given unusually beneficial results by way ofinhibiting deterioration of mineral hydrocarbon lubricating oil. This isdemonstrated inone instance by the following test data resulting fromcomparative Funk machine runs. There is likewise demonstrated thedistinction, in regard to inhibiting effectiveness, betweenanti-symmetrical compounds, such as the aforementioned, and relatedsymmetrical compounds such as beta beta di-naphthyl amine. The runs weremade with a turbine oil, produced from an East Texas crude petroleum,which oil had been refined by solvent extraction with liquid sulfurdioxide and had a viscosity at F. of

Saybolt seconds.

. Time to form 1% Inhibitor:

* (No evidence of sludge and emulsion formation at 2500 hours.)

A particular advantage of inhibitors according to the invention residesin the extremely small proportions necessary to effect very substantialinhibiting or stabilizing of the oil in respect of deteriorationthereof. This is aptly demonstrated by the foregoing data wherein 0.05%of alpha beta di-naphthyl amine is shown to occasion a remarkableincrease in the Funk life of the oil in question. It will be understood,of course, that larger or smaller proportions of inhibitor may be usedas deemed desirable but in general it is contemplated that the practiceof the invention will entail the use of amounts of the order of lessthan 1% and, in the interests of economy, less than 0.1%. Myinvestigations indicate that the potency of inhibitors, of ,thecharacter of alpha beta di-naphthyl amine, is such that proportions inthe range of 0.005% to 0.05% will in many cases be entirelysatisfactory.

The compounds which I have discovered to be of value as inhibitors forlubricating and like petroleum oils are readily soluble in the oil inproportions well in excess of the range indicated above as givingeffective stabilizing action. The invention may be practiced, therefore,either by the direct addition of inhibitor to oil in the desiredinhibiting proportion or, as may in many instances be preferable, bypreparing a concentrated solution comprising several percent ofinhibitor in oil and then adding a suitable amount of such concentrateto bulk quantities of oil.

Inhibitors within the contemplated scope and practice of the inventioninclude not only the straight di-aryl amines of anti-symmetricalstructure wherein both aryl groups are polycyclic aromatic rings, butalso derivatives thereof comprising such di-aryl amines wherein one ormore hydrogen atoms on one or both of the arcmatic nuclei is replaced bya substituent group. The substituting group may, for example, be oneselected from the class of aryl, alkyl, amino, aryloxy and alkyloxyradicals, but it is important to avoid the presence of substituentswhich would occasion undue decrease in oil solubility, increase in watersolubility, particularly if the inhibitor is to be used in turbine oilor like service where the presence of water is a service factor), orotherwise detracts from the useful effectiveness at the inhibitor.

The importance of an anti-symmetrical structure or molecular arrangementin inhibitors of the invention has been referred to. Ample evidenceof'this is afforded by the illustrative Funk test reported herein, wherethe data includes results with a symmetrical di-naphthyl amine forcomparison with those attending the use of an anti-symmetrical compound.The marked novelty and utility of the latter is apparent.

The use of inhibitors of the character of alpha beta'di-naphthyl amineand derivatives thereof according'to the invention is not confined tothe specific oil designated in the foregoing example. 75

Other mineral hydrocarbon oils of lubricating oil character may bestabilized against deterioration by the incorporation therewith of theseinhibiting compounds. Thus, the inhibitors of the invention may beapplied to the stabilization of oils having greater or less viscositythan 150 seconds Saybolt at 100 F.; and to such oils as refined byvarious methods alternative to extraction with liquid sulfur dioxide.However, the use of these inhibitors in technical white oils derivedfrom petroleum as by drastic refining with fuming sulfuric acid forms nopart of the present invention; nor does the present inventioncontemplate as within its intended scope or practice the use of thesecompounds as inhibitors of gum formation in cracked gasoline.

Evidence of the broad utility of inhibitors according to the inventionin its intended field of service is afforded by the results of anothertest method wherein internal combustion engine lubricants comprise theoil environment in which the inhibitors function. This test, describedbelow, is one devised in recent years to demonstrate both the tendencyof motor oils to deteriorate per se and their tendency to occasioncorrosion of bearing surfaces in internal combustion engines wherein thebearings are formed of, or surfaced with, cadmium-silver, cadmiumnickel,copper-lead and like alloys. The two said tendencies may or may not berelated, little being known concerning the nature of the corrosiveaction or its causes. It has been observed that motor oils derived fromselected crudes predominantly parafiinic in origin, as well as thoseoils from these or other crudes which have been improved by treatmentwith selective solvents, exhibit a marked tendency toward corrosion ofthe bearings in question, although by other tokens the lubricant is ofsuperior quality and is not corrosive toward bearing surfaces formed ofBabbitt metal. It is possible that the high bearing surface temperaturesexisting under service conditions with the newer bearingsformed ofcadmium-silver and like alloys may be a factor in occasioning theobserved deleterious effect of motor oils thereupon.

The aforementioned test, by which a comparative evaluation of motor oilsmay be obtained in the laboratory, is conducted as follows. A group ofbearings, ordinarily including at least one each of several of the newerbearing metal alloys (viz: cadmium-silver, cadmium-nickel andcopper-lead) is supported in a chamber in which air may circulate, andthe bearing surfaces are exposed for a period of 22 hours to a stream ofoil sprayed under pressure continuously upon the corrodible area. Theoil is maintained at a temperature of 335 F. and the spray is sodirected as to disperse the oil over the surfaces of the bearings. Meansare provided for re-circulating the sprayed oil so that a given quantityis used for a given test, thus simulating service conditions in anengine. The measure of corrosion is taken as the loss in weight of thebearing per unit of exposed corrodible surface. Coincidently, a measureof oil deterioration per se is obtained by observing or determining theneutralization number of the oil after a test run as well as suchfactors as the increase in viscosity and carbon residue.

The test method described above is carried out in the familiar Underwoodcorrosion apparatus supplied by the Scientific Instrument Company ofDetroit, Michigan, in accordance with General Motors specifications.

-a viscosity at 210 F. of 54 Saybolt seconds, and

a carbon residue of 0.39%. It comprised a blend of solvent refinedPennsylvania neutral oil with conventionally produced Pennsylvaniabright stock. A sample of this oil was submitted to test according to aprocedure as hereinbefore outlined wherein cadmium-silver,cadmium-nickel and copper-lead bearings were used. The loss in weightper square decimeter due to corrosion was as follows for the respectivebearings:

' Grams Cadmium-silver -1 6.7 Cadmium-nickel 3 .8 Copper-lead 1.0

The used oil after the run showed a 47% increase in the Sayboltviscosity at 210 R, an increase in carbon residue from 0.39 to 3.41, anda neutralization number of 4.5 milligrams KOH per gram of oil.

There was then incorporated with a fresh supply of the foregoing motoroil an inhibitor according to the invention comprising alpha betadi-naphthyl amine in the amount of 0.2% by weight, and this inhibitorcontaining oil subjected to test according to the indicated procedure.The results indicated a complete suppression of bearing corrosion, noloss in weight for any of the three types of bearing being observed.Regarding deterioration of the oil itself, substantial benefit resultedfrom the presence of the inhibitor, the increase in viscosity at 210 F.

' being but 9% instead of 4'7 for the oil without inhibitor, the carbonresidue increasing only to 1.27, and the used oil showing aneutralization number of 1.1 milligrams KOH per gram of oil as. comparedwith 4.5 in the blank run.

Further investigations utilizing the foregoing motor oil test for theevaluation of inhibitors according to the invention emphasized themarked superiority of anti-symmetrical compounds over those of asymmetrical arrangement. Thus, when 0.2% by weight of alpha alphadi-naphthyl amine was used in place of 0.2% by weight of alpha betadi-naphthyl amine, bearing corrosion losses as follows were observed:

Grams Cadmium-silver; 6.4 Cadmium-nickel 8.0 Copper-lead 0.5

Coniparing the abovewith the corrosion lossesinduced by the oil withoutinhibitor, it will be noted that the cadmium-silver bearing underwentsubstantially the same degree of corrosion, and that while the corrosionof the copper-lead bearing appeared to be somewhat retarded, thesymmetrical compound actually accelerated in marked degree the corrosionof the cadmiumnickel bearing. The carbon residue of the used oil in thisrun was 3.07, very nearly as high as that of the used oil in the runwithout innibitor; and a neutralization number of 6.94 milligrams KOHper gram of used oil indicated an accelerated deterioration of the oilitself.

The assembled evidence of all of the foregoing data and results obtainedin the several comparative tests demonstrates the advantagesattendingthe use of inhibitors comprising anti-symmetrical diarylamineswherein both aryl groups are condensed rings.

I claim:

1. Mineral oil composition comprising a viscous hydrocarbon oil normallytending to deteriorate in service and having incorporated therewithdeterioration inhibiting proportions of an anti-symmetrical di-arylamine wherein both aryl groups are polycyclic or substituted polycyclicaromatic rings.

2. Mineral oil composition comprising a viscous hydrocarbon oil normallytending to deteriorate in service and having incorporated therewithdeterioration inhibiting proportions of an anti-symmetrical di-arylamine wherein both aryl groups are polycyclic-aromatic rings.

3. Mineral oil composition comprising a viscous hydrocarbon oil normallytending to deteriorate in service and having incorporated therewithdeterioration inhibiting proportions of alpha beta di-naphthyl amine.

4. Refined turbine oil, normally tending toward acid, sludgeor emulsionformation in service, having incorporated therewith inhibitingproportions of an anti-symmetrical di-aryl amine 5. Refined turbine oil,normally tending toward acid, sludge or emulsion formation in service,

' having incorporatedtherewith inhibiting proportions of alpha betadi-naphthyl amine.

6. Mineral oil composition, comprising a hydrocarbon lubricating oil ofmotor oil character normally tending to corrode the type of bearingmetal exemplified by cadmium-silver, cadmiumnickel and copper-leadalloys when continuously applied to the surface thereof for an extendedperiod of time at an oil temperature of 335 F., and an anti-symmetricaldi-aryl amine wherein both aryl groups are polycyclic aromatic ringsincorporated with said oil in corrosion inhibiting proportions. p

7. Mineral oil composition, comprising a hydrocarbon lubricating oil ofmotor oil character normally tending'to corrode the type of bearingmetal exemplified by cadmium-silver, cadmium nickel and copper-leadalloys when continuously applied to the surface thereof for an extendedperiod of time at an oil temperature of 335 F., and alpha betadi-naphthyl amine incorporated with said oil in corrosion inhibitingproportions.

ELMER WILLIAM COOK.

